It is not uncommon to hear many individuals assert that they have unusually sensitive skin. In such cases, the afflicted individual frequently reports itching, burning or stinging as the result of an identifiable event, such as applying a specific material to the skin; however, a similar reaction may also be reported as a response to a non-specific environmental stimulus. In either case, the reaction causes significant, and regular, discomfort to those individuals so afflicted.
In the case of a specific product causing the stinging reaction, the stinging potential of the product is frequently not even apparent upon initial testing. It is not uncommon that a product for topical application will pass all standard tests for topical safety, yet when in general distribution, the product will elicit a number of complaints from a substantial percentage of users. Those who report "subjective" stinging exhibit no objectively observable physical symptoms upon exposure to certain types of external stimuli, yet consistently and reliably report discomfort upon such exposure. It is now generally accepted that there is a fairly sizable subpopulation within the general population who can be defined as "stingers", i.e., who have a very delicate or hypersensitive skin (Frosch and Kligman, J. Soc. Cosm. Chem. 28: 197, 1977). The phenomenon is frequently referred to as "lactic acid stinging", in reference to the substance that is frequently used to elicit this reaction in objective testing so as to identify sensitive individuals. The physiological basis for this response is at the present time still a mystery. However, there appear to be no reliable phenotypic indicia which permit the a priori identification of "stingers" in the population.
The stinging problem is clearly one that affects both the consumer and the manufacturers of topically applied products. The highly sensitive consumer is often deprived of the benefits of many useful products because of the irritation experienced upon use. The manufacturer in turn is hampered by the necessity for extensive, and expensive, testing to identify materials in formulation which may cause stinging, and even then, will be unable to identify that small, but significant, subpopulation of users who will be affected by potentially stinging material. Thus, considerable research and development efforts may be invested in a product which will be unusable by a substantial percentage of the intended users. It would, therefore, be beneficial to determine a means by which the stinging potential of certain products can be reduced, and/or by which the stinging subset of the population can be treated to reduce the propensity to stinging. The present invention provides such a means.